Sorry I'm late on this one, but I hope I can help seeing as I worked for a company that framed pictures. (No, buttmunch, not a kwikky-frame type outlet, this did the real McCoy, framing like 100000000000+ originals and restoring those 10-inch thick nasty big frames from 'Country Houses' and museums and the like. Still got the scar on my thumb from where I chopped the tip off concentrating on a VERY expensive bit of frame while cutting it.....a couple of hundred quid a foot it was, really special stuff.....looked crap though.) Anyways, this may be out of date and not 'chic' as it was way back then (16 years or so), but in general if it was an original the artist would sign the print. The medium used to sign and how much it showed depended on how 'flashy' the artist was and how much they wanted people to notice it. "Prints" on the other hand (ie, reprints of the original picture by a printing company as opposed to the artist) generally showed the signature already from the original and would therefore be signed on the 'mating' (snigger) or the board on the back of the frame if a sticker or something similar was used to show the authenticity and number. As for the air getting to it I personally wouldn't worry too much about that anyways - from what little I know of inks, most of the damage is probably done within the first few minutes of it being printed as it dries.... Regarding the back of the picture, I would personally always use the gummed paper around the edge. No matter how good the frame makers are, it still looks neater. Plus in the future when they become valuable (ie. after you die, usually) it means someone will be pleased that the valuer is easily able to tell that the picture hasn't been tampered with in any way....... If you want to have a chuckle to yourself, hand-scribble a message on a bit of paper and put it in with the print... different message every time..... then seal it ;) If you ever do get famous you can let people know that the messages exist, and have them battle with their own curiosity to see what they say vs devaluing the picture... ROFL.... (",)